loop safe wrapper for dbGet added

dirk-zimoch · Nov 29, 2024 · e206843 · e206843
1 parent 1567da1
commit e206843
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Showing 2 changed files with 43 additions and 30 deletions.
diff --git a/modules/database/src/ioc/db/dbDbLink.c b/modules/database/src/ioc/db/dbDbLink.c
@@ -103,6 +103,7 @@ long dbDbInitLink(struct link *plink, short dbfType)
     plink->lset = &dbDb_lset;
     plink->type = DB_LINK;
     plink->value.pv_link.pvt = chan;
+    plink->flags &= ~(DBLINK_FLAG_VISITED|DBLINK_FLAG_LOOPS|DBLINK_FLAG_LOOPFREE);
     ellAdd(&precord->bklnk, &plink->value.pv_link.backlinknode);
     /* merging into the same lockset is deferred to the caller.
      * cf. initPVLinks()
@@ -232,19 +233,48 @@ static long dbDbGetValue(struct link *plink, short dbrType, void *pbuffer,
     return status;
 }
 
-static long dbDbGetControlLimits(const struct link *plink, double *low,
-        double *high)
+/* Some records get options (precsision, units, ...) for some fields
+ * from an input link. We need to catch the case that this link
+ * points back to the same field or we will end in an infinite recursion.  
+*/
+static long dbGetLoopSafe(const struct link *plink, short dbrType,
+    void *pbuffer, long option)
 {
+    /* We need to cast away const.
+       That's ok because we know that plink is never actually readonly.
+    */
+    struct link *mutable_plink = (struct link *)plink;
+    long status = S_dbLib_badLink;
     dbChannel *chan = linkChannel(plink);
     DBADDR *paddr = &chan->addr;
+    long number_elements = 0;
+
+    if (plink->flags & DBLINK_FLAG_LOOPS)
+        return status;
+    if (!(plink->flags & DBLINK_FLAG_LOOPFREE))
+        return dbGet(paddr, dbrType, pbuffer, &option, &number_elements, NULL);
+    dbScanLock(paddr->precord);
+    if (mutable_plink->flags & DBLINK_FLAG_VISITED) {
+        mutable_plink->flags |= DBLINK_FLAG_LOOPS;
+    } else {
+        mutable_plink->flags |= DBLINK_FLAG_VISITED;
+        status = dbGet(paddr, dbrType, pbuffer, &option, &number_elements, NULL);
+        if (!(mutable_plink->flags & DBLINK_FLAG_LOOPS))
+            mutable_plink->flags |= DBLINK_FLAG_LOOPFREE;
+        mutable_plink->flags &= ~DBLINK_FLAG_VISITED;
+    }
+    dbScanUnlock(paddr->precord);
+    return status;
+}
+
+static long dbDbGetControlLimits(const struct link *plink, double *low,
+        double *high)
+{
     struct buffer {
         DBRctrlDouble
         double value;
     } buffer;
-    long options = DBR_CTRL_DOUBLE;
-    long number_elements = 0;
-    long status = dbGet(paddr, DBR_DOUBLE, &buffer, &options, &number_elements,
-            NULL);
+    long status = dbGetLoopSafe(plink, DBR_DOUBLE, &buffer, DBR_CTRL_DOUBLE);
 
     if (status)
         return status;
@@ -257,16 +287,11 @@ static long dbDbGetControlLimits(const struct link *plink, double *low,
 static long dbDbGetGraphicLimits(const struct link *plink, double *low,
         double *high)
 {
-    dbChannel *chan = linkChannel(plink);
-    DBADDR *paddr = &chan->addr;
     struct buffer {
         DBRgrDouble
         double value;
     } buffer;
-    long options = DBR_GR_DOUBLE;
-    long number_elements = 0;
-    long status = dbGet(paddr, DBR_DOUBLE, &buffer, &options, &number_elements,
-            NULL);
+    long status = dbGetLoopSafe(plink, DBR_DOUBLE, &buffer, DBR_GR_DOUBLE);
 
     if (status)
         return status;
@@ -279,16 +304,11 @@ static long dbDbGetGraphicLimits(const struct link *plink, double *low,
 static long dbDbGetAlarmLimits(const struct link *plink, double *lolo,
         double *low, double *high, double *hihi)
 {
-    dbChannel *chan = linkChannel(plink);
-    DBADDR *paddr = &chan->addr;
     struct buffer {
         DBRalDouble
         double value;
     } buffer;
-    long options = DBR_AL_DOUBLE;
-    long number_elements = 0;
-    long status = dbGet(paddr, DBR_DOUBLE, &buffer, &options, &number_elements,
-            0);
+    long status = dbGetLoopSafe(plink, DBR_DOUBLE, &buffer, DBR_AL_DOUBLE);
 
     if (status)
         return status;
@@ -302,16 +322,11 @@ static long dbDbGetAlarmLimits(const struct link *plink, double *lolo,
 
 static long dbDbGetPrecision(const struct link *plink, short *precision)
 {
-    dbChannel *chan = linkChannel(plink);
-    DBADDR *paddr = &chan->addr;
     struct buffer {
         DBRprecision
         double value;
     } buffer;
-    long options = DBR_PRECISION;
-    long number_elements = 0;
-    long status = dbGet(paddr, DBR_DOUBLE, &buffer, &options, &number_elements,
-            0);
+    long status = dbGetLoopSafe(plink, DBR_DOUBLE, &buffer, DBR_PRECISION);
 
     if (status)
         return status;
@@ -322,16 +337,11 @@ static long dbDbGetPrecision(const struct link *plink, short *precision)
 
 static long dbDbGetUnits(const struct link *plink, char *units, int unitsSize)
 {
-    dbChannel *chan = linkChannel(plink);
-    DBADDR *paddr = &chan->addr;
     struct buffer {
         DBRunits
         double value;
     } buffer;
-    long options = DBR_UNITS;
-    long number_elements = 0;
-    long status = dbGet(paddr, DBR_DOUBLE, &buffer, &options, &number_elements,
-            0);
+    long status = dbGetLoopSafe(plink, DBR_DOUBLE, &buffer, DBR_UNITS);
 
     if (status)
         return status;

diff --git a/modules/database/src/ioc/dbStatic/link.h b/modules/database/src/ioc/dbStatic/link.h
@@ -72,6 +72,9 @@ DBCORE_API extern const maplinkType pamaplinkType[LINK_NTYPES];
 /* DBLINK Flag bits */
 #define DBLINK_FLAG_INITIALIZED    1 /* dbInitLink() called */
 #define DBLINK_FLAG_TSELisTIME     2 /* Use TSEL to get timeStamp */
+#define DBLINK_FLAG_VISITED        4 /* Used in loop detection */
+#define DBLINK_FLAG_LOOPS          8 /* Used in loop detection */
+#define DBLINK_FLAG_LOOPFREE      16 /* Used in loop detection */
 
 struct macro_link {
     char *macroStr;